Method for the preparation of cyclohexene-4-carboxylic acids



Patented Sept. 22, 1953 umrr. so TAT E1 T OFFICE JMETHOD FOR THE PREPARATION OF cycLonsxsNsa-ciineoxy rc cros LJacobEden Jansen, Akron, and Erankxwwerber, North Royalton, Ohio, assignors -to Tl1e Goodrich Company, New York, N. Y.,a corny;-

-ration of New York No Drawing. Application July 18, 1951, t 'Serial No. 237,478

,10 Claims. (01. 260-51 4;)

the reaction of a ketene with an aldehyde or "-ketone. In this manner beta-propiolactone (also called hydracrylic acid lactone), which has the .formula QH2 OHz-G=0 1' is -.economicallyobtained from ketene and form- :aldehyde. The 'easeawith which beta -propio- Jlactone and other-lactones are ,now obtained remakes it desirable tense-these compounds as "starting materials in the 'ynthesis of many :other useful compounds.

It has now been discovered thatheta-lactones and beta-lactone polymers v undergo a 'Diels- Alder reaction with conjugated v;;po lyenes -s u c h as butadiene-1,3 to. give cyclohexene-4-carboxylic :acids which are very valuable in organic synthesis. For example, aliphatic dicarboxylic :xacids are obtained byzalkaline isomerization and l cleavage of .the;cyclohexene ring. Esters of the ="dicarboxylic' acidsobtainedwin this manner are a useful as. plasticizers forsynthetic resins and rub- ".lbers,1and as additives .for lubricating oils. The

KCYClOhGXBHS ring :of' the ,adducts may also be '1 .split'by oxidationrto give .tricarboxylicacids and .:.may.:be-.reduced.to give cyclohexane carboxylic' acids which are ;useful...as. selective herbicides.

.LMoreover, the L.cyclohexeneA-carboxylic acids 4 are. useful per se, as insecticides, fungicides, and iLfOl" many other, purposes.

:The Diels-Alder reaction of beta-lactones with polyenes "according vto" :this invention proceeds :substantially as shown. by the following equation, wherein the most simple diene, butadiene- 1,3; is used for illustrative purposes:

-"The term alicyclicwherever used hereinafter is alpha methyl wherein R1, R2 and R3 .representuhydrogen, alkyl,

,aralkyl, aryl or substitute d 'alkyl, a'rylor aralkyl radicals.

The beta-,lactone employedmay ,be any lactone of a beta-hydroxy mqnolcarboxylic acid which has at least one hydrogen atom on'the alpha carbon atom for example, beta-lactones of saturated aliphatic monocarboxylic "acids ,such as beta-pr'opiolactone, {beta-butyrmactone, "alphamethyl beta-propiolactone', beta-h-valerolactone, betabutyrolactone, alpha-ethyl beta-propiolactone, alpha-methyl beta-valerolactone, beta-methyl beta-ethyl beta-propiolactone, alpha-propyl beta-propiolactone, alphabutyl beta-methyl beta propiolactone, or the like as well as polymers of such beta-lactones; betalactones of substituted'carboxylicacids such as beta-phenyl beta-propiolactone, alpha-phenyl beta-propiolactone, ,tbeta chloroethyl beta-prop iolactone, beta benzyl beta propiolactone, alpha benzyl beta propiolactone, beta cyclohexyl beta-propiolactoneand the like and polymers of these .beta-lactones, as. well as other beta-lactones andbeta-lactone polymers of. the

. nature hereinab ove s et' forth. Especially preferred beta-lactones forusenin the practice of this invention aresthe saturated aliphatic beta- -lactones; that is, those betal-lactones wherein -R1,- R2 and Rain the above formula represent hydrogen oran alkyl radical, with the watersoluble saturated-alphatic beta-.lac'tones forming a particularly preferred class of beta-lactones; those beta-lactones which contain from 3 to 6. carbon atoms possess the property of being water-soluble.

The 1 13161 6 which is reacted with the betalactone to form a cyclohexene--carboxylic acid may be any conjugated acylicor alicyclic polyene'capable offorming a-Diels-Alder adduct and preferably containing from 4lto 10 carbon atoms.

intended to encompass compounds which contain a :ringpf carbon atoms but whichdo not ipiperylene, 3 methylpentadiene 1,3,

belong to;.the aromatic series. Included among such polyenes are thefollowing:

Acyclic or conjugated polyenes such as butadiene-l,3, isoprene, Z-methylpentadiene-LB,

- smethyl-butadiene-lfi, j 2- neopentylbutadiene-1,3,

l-phenylbutadieneelfl- Z-phenyIbutadiene-LS,

2-chlorobutadienes1,3, 2-bromobutadiene-1,3, 2-

fluorobutadiene-1,3, -heXadiene-2,4,-' hexatriene- 1,3,5, 2-methylhezgat riene-1,3,5, 1,6-diphenylh t nalfifii.re reenee wa m e a the 3 Alicyclic conjugated polyenes such as cyclopentadiene, cyclohexadiene, cycloheptadiene,

As disclosed hereinabove, both beta-lactones and beta-lactone polymers react with conjugated polyenes in accordance with the present invention. Beta-lactone polymers are readily prepared simply by heating the beta-lactone either alone or in the presence of a catalyst such as an acid or base or a metal salt. Beta-lactone polymers vary in character from colorless, viscous oils to white solids depending on their molecular weight, the higher molecular weight polymers being solid in nature.

The relative amounts of beta-lactone and polyene utilized in carrying out the process of this invention may be varied widely. For example, the reactants may be brought together in equimolar quantities, or a stoichiometric excess of either reactant may be used; in general, however, it has been found that optimum yields of the cyclohexene-4-carboxylic acid are obtained when a slight excess of the conjugated polyene is used, for example, about 1.1 to 1.5 moles of the polyene for each mole of the beta-lactone or for each lactone unit in the beta-lactone polymer.

The reaction is best carried out by first placing the beta-lactone or beta-lactone polymer in a pressure reactor such as an autoclave, and adding the conjugated polyene, which is ordinarily a gas or liquid and is therefore most easily pumped into the reactor. The reactants are then heated at 100 to 250 C. and at autogenous pressures for approximately 1 to 2 hours whereupon. reaction occurs to form the desired cyclohexene- 4-carboxylic acid. Generally equivalent results are obtained by reversing the order of addition, that is, by adding the beta-lactone or beta-lactone polymer to the polyene reactant. The prodnot can be recovered in substantially pure form simply by distilling the reaction mixture, preferably at reduced pressures.

When beta-lactone polymer is to be used in the process of this invention a desirable expedient consists in placing the monomeric beta-lactone and polymerization catalyst in the autoclave and carrying out the polymerization and subsequent reaction with the conjugated polyene in situ. It is also desirable that a polymerization inhibitor such as hydroquinone or tertiary butyl catechol. be added to the reaction mixture to prevent polymerization of the monomeric materials present therein.

Although no catalyst is necessary in the process of this invention, catalytic quantities of an alkaline material such as alkali metal hydroxides and alkali metal carbonates are advantageously utilized to accelerate the reaction. Acidic materials and metal salts may also be present in catalytic quantities during the process.

The method of reacting beta-lactones and betalactone polymers with polyenes in accordance with the process of the present invention is set forth more fully in the following examples which are intended as illustrative only since numerous modifications and variations therein will be apparent to those skilled in the art. In the examples all parts are by Weight.

Example I 4 dime-1,3 6 parts of potassium carbonate and 2 parts of hydroquinone are placed in a stainless steel autoclave and the mixture heated to about 200 C.; exothermic reactions take place at about C. and 200 C., raising the temperature to 270 C. for a short time. The temperature is then maintained at 200 C. for 1.5 hours after which the crude reaction product is distilled; and 937 parts (96% based on the beta-propiolactone content of the starting material) of cyclohexene- 4-carboxylic acid are obtained. (B. P. 126

C./16 mm., 123 C./13 mm.; N =1.4780; 114 10715; M. P. 15.0 C.)

Example II 5 parts of potassium carbonate and 1 part of hydroquinone are heated to 170 C. in a stainless steel autoclave. A mixture of 432 parts betapropiolactone (97% purity, 5.82 moles) and 476 parts (7.0 moles) of isoprene is then pumped into the autoclave. The temperature rises to 205 C. and is maintained at that point for 1 hour. Distillation of the resulting reaction mixture gives 750 parts (92%) of a mixture of methyl cyclohexene-e-carboxylic acids (B. P. 93 C./O.9 mm.; 129 C./10 mm.; M. P. 7590 0.; believed to be predominantly the para isomer, l-methyl cyclohexene-a-carboxylic acid).

Example III A mixture of 241 parts of beta-propiolactone (97% purity, 3.25 moles) and 300 parts of dicyclopentadiene (which changes into cyclopentadiene at the reaction temperature) are pumped into a stainless steel reaction bomb containing 5 parts of potassium carbonate and 7 parts of hydroquinone, the bomb being maintained at a temperature of 180 C. After 1.25 hours the crude reaction product is distilled to give 3,6-endo methylene cyclohexene-e-carboxylic acid resulting from the reaction of cyclopentadiene with beta-propiolactone, in a yield of 415.3 parts (925%, based on weight of the beta-lactone). The product boils at 120.5-121.5 C./10 mm.; literature value, 132-434. C./22 mm.

Example IV Beta-propiolactone polymer is prepared by heating the lactone in the presence of copper acetate. 167 parts of the polymer thus prepared is charged, together with 138 parts (2.56 moles) of butadiene-1,3 and 1.0 part of hydroquinone into a stainless steel rocking autoclave which is first purged with nitrogen; the autoclave is then sealed, the rocker started and the bomb heated to about C. at which point an exothermic reaction takes place and the temperature rises to a maximum of. 191 C. The'bomb is then opened and the reaction mixture distilled whereupon 228 parts (79%) of cyclohexenel-carboxylic acid are obtained. (B. P. 132 C./21 mm.; M. P. 15 C.; d4 =l.0715 and m =1.4771.)

Example V 5 parts of potassium carbonate and 1 part of hydroquinone are heated to C. in a stainless steel autoclave. A mixture of 432 parts of betapropiolactone and 476 parts of isoprene are then pumped into the autoclave over a 1 hour period during which time the temperature rises to 205 C. The reaction mixture is then distilled Whereupon 750 parts (92% of theory) of a mixture of isomeric methyl cyclohexene--carboxylic acids (B. P. 93 C./0.9mm.; 129 C./10 mm.) are obtained.

When this example is repeated substituting beta-butyrolactone for the beta-propiolactone, 5- methyl cyclohexene--carboxylic acid is obtained in good yield. Moreover, when the examples are repeated utilizing other of the beta-lactones having at least one hydrogen atom attached to the alpha-carbon atom, or substituting other of the polyenes disclosed hereinabove for those utilized in the examples, cyclohexenei-carboxylic acids are again obtained.

From the foregoing description of the invention, it will be seen that the reaction of beta-lactones with conjugated polyenes constitutes a new, improved and economical method for producing cyclohexene--carboxylic acids, a widely useful class of materials. It is apparent, therefore, that various embodiments of the invention, in addition to those specifically disclosed, may be provided without departing from the spirit and scope of the invention as defined in the appended claims.

We claim:

1. The method which comprises reacting a member of the class consisting of beta-lactones having at least one hydrogen atom on the alpha carbon atom, and homopolymers of said betalactones, with a member of the class consisting of acyclic and alicyclic polyenes, at a temperature of from about 100 C. to 250 0., thereby to obtain a cyclohexenel-carboxylic acid.

2. The method which comprises reacting a member of the class consisting of beta-lactones having at least one hydrogen atom on the alpha carbon atom, and homopolymers of said betalactones, with an acyclic conjugated diene, at a temperature of from about 100 C. to 250 0., thereby to obtain a cyclohexene-4-carboxylic acid.

3. The method which comprises reacting a member of the class consisting of beta-lactones having at least one hydrogen atom on the alpha carbon atom, and homopolymers of said betalactones, with an alicyclic conjugated diene, at a temperature of from about 100 C. to 250 C., thereby to obtain a cyclohexene-4-carboxylic acid.

4. The method which comprises reacting at autogenous pressure a saturated aliphatic betalactone and an acyclic conjugated diene, at a temperature of from about C. to 250 0., thereby to obtain a cycloheXenei-carboxylic acid.

5. The method which comprises reacting at autogenous pressure, at a temperature of about 100 C. to 250 C. and in the presence of an alkali metal carbonate, a saturated aliphatic betalactone and an acyclic conjugated diene, and distilling the resulting reaction mixture, thereby to obtain a cyclohexene-4-carboxy1ic acid,

6. The method of claim 5 wherein the betalactone utilized is beta-propiolactone and the acyclic conjugated diene is butadiene-l,3, the product recovered being cyclohexene-4-carboxylic acid.

7. The method of claim 5 wherein the betalactone utilized is beta-propiolactone and the acyclic conjugated diene is 2-methyl butadiene- 1,3, the product recovered being a mixture of 1- methyl cyclohexenei-carboxylic acid and 2- methyl cyclohexene-4-carboxylic acid.

8. The method which comprises reacting at autogenous pressure a saturated aliphatic betalactone and an alicyclic conjugated diene, at a temperature of from about 100 C. to 250 0., thereby to obtain a cyclohexene-i-carboxylic acid.

9. The method which comprises bringing together at autogenous pressure, at a temperature of about 100 C. to 250 C. and in the presence of an alkali metal carbonate, a saturated aliphatic beta-lactone and an alicyclic conjugated diene, and distilling the resulting reaction mixture, thereby to obtain a cyclohexene-i-carboxylic acid.

10. The method of claim 8 wherein the betalactone utilized is beta-propiolactone and the alicyclic conjugated diene is dicyclopentadiene, the product recovered being 3,6-endomethylene cyc1ohexen-4-carboxylic acid.

JACOB EDEN JANSEN. FRANK X. WERBER.

References Cited in the file of this patent UNITED STATES PATENTS Number 

1. THE METHOD WHICH COMPRISES REACTING A MEMBER OF THE CLASS CONSISTING OF BETA-LACTONES HAVING AT LEAST ONE HYDROGEN ATOM ON THE ALPHA CARBON ATOM, AND HOMOPOLYMERS OF SAID BETALACTONES, WITH A MEMBER OF THE CLASS CONSISTING OF ACYCLIC AND ALICYCLIC POLYENES, AT A TEMPERATURE OF FROM ABOUT 100* C. TO 250* C. THEREBY TO OBTAIN A CYCLOHEXENE-4-CARBOXYLIC ACID 